Bonding abrasive tools, which usually refer to abrasive wheels, generally consist of an abrasive substrate layer or grinding layer, and a fiberglass reinforced mesh (also called a “fiber reinforced mesh”). Among them, a common effective means to improve the toughness of abrasive wheels, especially resin abrasive wheels, is to use a fiber reinforced mesh as a reinforcement substrate. The fiberglass reinforced mesh functions to improve the toughness of the abrasive wheel to ensure safe operation, so that in high speed rotation, the abrasive wheel will not burst as a result of the centrifugal force to threaten the life and safety of operators. Therefore, the fiberglass reinforced mesh is a reinforcement substrate that is essential in bonding abrasive tools.
In the prior art, the fiberglass reinforced mesh is prepared through a dipping process, in which a woven fiberglass fabric is dipped into a resin sizing agent and, after drying, and dried fiberglass reinforced mesh has a fiber fabric layer in the middle and resin layers on the upper and lower surfaces. A resin layer, also called a combustible layer, is generally formed by solidifying a thermoset resin such as epoxy resin or phenolic resin together with a solvent, a surfactant, and an aid and the like. For those skilled in the art, the resin layer is essential and must have a certain thickness, as it has the following functions:
1. it provides a strong texture interface after the fiberglass reinforced mesh is solidified so as to enhance the hardness of the fiberglass reinforced mesh;
2. it ensures that the fiberglass reinforced mesh meets the process requirements, that is to say, possesses a certain toughness and flatness;
3. in pressing the abrasive wheel, it protects the fiberglass fabric from being squeezed and thus damaged by abrasive particles;
4. it provides chemical bonds to effectively bind the abrasive substrate with the fiberglass fabric.
Therefore, the structure of the fiberglass reinforced mesh of the prior art is as follows:
1. it has a fiberglass fabric layer;
2. the fiberglass fabric layer is coated with phenolic resin on either surface through the dipping process;
3. in the fiberglass mesh, the weight of the resin material per m2 shall be more than 90 g (or called “resin content” hereinbelow, unit: g/m2);
4. the combustible content in the fiberglass mesh (i.e., the weight percentage of the solidified dip coating relative to the whole mesh, or the weight percentage of the resin relative to the whole mesh, both of which are referred to as “resin content” hereinbelow for convenience of understanding) shall be in the range of more than 30%.
According to the above description of existing technical solutions, the fiberglass mesh must comprise a relatively high resin content for the reason that the burst speed and the grinding rate (removal amount of materials/wear extent of abrasive wheel) are two important performance indexes for abrasive wheels, especially thin abrasive wheels, and in order that the abrasive wheel does not burst at a high rotation speed, the abrasive wheel, especially the thin abrasive wheel, must be reinforced through a fiberglass mesh coated with a phenol-based dip coating. In practice, the content of the resin material is at least more than 90 g/m2 in the fiber reinforced mesh, and is about 100 g/m2 in common fiber reinforced meshes. The resin content per unit area may be measured by the following method. According to current national standards relating to the mechanical industry in China, the fiber reinforced mesh for bonding abrasive tools shall have a resin content of not less than 28%. The resin content may be measured by the following method.
The mass of a fiberglass reinforced mesh sample is weighed and marked as W1. The sample is placed into a cabinet drier where it is dried at 160° C.±2° C. for 20 minutes, removed, and then placed into a drier to cool down to room temperature. The mass of the sample is weighed and marked as W2. Then, the sample is placed into a high temperature furnace where it is ignited at 600° C.±20° C. for 1 hour, removed and then placed into a drier to cool down to room temperature. The mass of the sample is weighed and marked as W3. The resin weight per unit area of the fiberglass reinforced mesh is calculated by a formula as follows:Resin weight(resin content)per unit area=(W1−W3)/mesh area
As conceived by those skilled in the art, the fiberglass can have a certain rigidity and interfacial strength and the abrasive wheel can possess a reliable burst speed only when the weight of the resin material per m2 of the fiber reinforced mesh on average is at least more than 90 g.Combustible content(resin content)=(W1−W3)/W1×100%
As conceived by those skilled in the art, a resin content of more than 28% can provide the fiberglass with a certain rigidity and interfacial strength and ensure that the abrasive wheel possesses a reliable burst speed.
Furthermore, in current production practices, the glass reinforced mesh for abrasive wheels has a resin content of 33%±3%.
However, the fiberglass reinforced mesh of the prior art has the following deficiencies:
1. The costs of raw materials are high. It is widely believed by those skilled in the art that, in order to ensure the reliability and toughness of the abrasive wheel, the resin content of its fiberglass mesh shall be at least more than 90 g/m2, so a great deal of resin is coated on the fiberglass fabric layer. It is widely believed by those skilled in the art that, in order to ensure the reliability and toughness of the abrasive wheel, the resin content of its fiberglass mesh shall not be less than 28%, so a great deal of resin is coated on the fiberglass fabric layer. The costs of resin generally account for 30-50% of the costs of the fiberglass reinforced mesh, while the costs of the fiberglass reinforced mesh in turn account for 20-40% of the costs of the abrasive wheel.
2. The fiberglass mesh is coated with much resin and thus is overall relatively thick. As a result, abrasive wheels, especially thin abrasive wheel, in fabrication cannot be thinner (thinner abrasive wheels can save materials to be processed in metal processing, which is especially important in noble metal processing); or, in order to ensure the thickness, adding sufficient substrate materials in the abrasive substrate layer has to be given up or cannot be achieved.
3. The excessive use of resin layer material pollutes the environment and adversely affects human health, because thermoset resins such as phenolic resin release formaldehyde and other toxic volatile compound gases.